[Bug 222377] ZFS ABD wasteful...

bugzilla-noreply at freebsd.org bugzilla-noreply at freebsd.org
Sat Sep 16 23:20:42 UTC 2017


https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222377

            Bug ID: 222377
           Summary: ZFS ABD wasteful...
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: sean at chittenden.org

Created attachment 186440
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=186440&action=edit
ABD chunk size 1K

ABD was developed by Delphix and spent most of its life in testing with a value
of 1024.  Late in the review process over at OpenZFS the value was bumped to 4K
under the auspices of "page-aligned memory allocations perform better,"[1]
which is frequently true, however under production workloads we have found this
to be very wasteful.  The original 1K value should be restored and pushed
upstream into OpenZFS.  This change has already been made in Joyent's branch of
Illumos[2].

https://github.com/openzfs/openzfs/pull/326#issuecomment-291223116

https://github.com/joyent/illumos-joyent/commit/09443b7960ae0f0a3ddcf56d1879e006c2790316

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